The AH-64 Apache is a four-blade, twin-engine attack helicopter with reverse-tricycle landing gear, and tandem cockpit for a crew of two. The Apache was developed as Model 77 by Hughes Helicopters for the United States Army's Advanced Attack Helicopter program.

The Westland WAH-64 Apache is a licence-built version of the Boeing AH-64D Apache Longbow attack helicopter for the British Army. The first eight helicopters were built by Boeing; the remaining 59 were assembled by Westland Helicopters, from Boeing-supplied kits. Changes from the AH-64D include Rolls-Royce engines and a folding blade mechanism allowing the British version to operate from ships. The WAH-64 is designated Apache AH Mk 1 or AH1 by the UK's Ministry of Defence.